Current Follower Transconductance Amplifier Research Articles

On Approach to Increase Density of Fieldeffect Heterotransistors in the Framework of a Current Follower Transconductance Amplifier. Influence of Mismatchinduced Stress and Porosity of Materials on Technological Process

In this paper we introduce an approach to increase density of field-effect heterotransistors in the framework of a current follower transconductance amplifier. In the framework of the approach we consider manufacturing the amplifier in heterostructure with specific configuration. Several required areas of the heterostructure should be doped by diffusion or ion implantation. After that dopant and radiation defects should by annealed framework optimized scheme. We also consider an approach to decrease value of mismatch-induced stress in the considered heterostructure. We introduce an analytical approach to analyze mass and heat transport in heterostructures during manufacturing of integrated circuits with account mismatch-induced stress.

Current and transconductance mode full/half‐wave rectifiers realized with only one active block

SummaryThis research paper introduces a novel active building block for full/half‐wave (inverse) rectifier circuits, eliminating the need for passive elements. The paper presents two alternative implementations: a current mode approach utilizing MO‐CFTA (multiple output current follower transconductance amplifier) and a transconductance mode approach utilizing MO‐VDTA (multiple output voltage differencing transconductance amplifier). Both circuit configurations exhibit favorable zero‐crossing characteristics and exceptional linearity. The transconductance mode rectifier enables electronic control of the output current signal by adjusting the applied bias currents. The circuits are designed with simplicity and compactness in mind, making them highly suitable for integration into IC circuits. The analysis investigates the impact of non‐idealities and parasitic effects, although the absence of passive elements results in minimal parasitic effects. Simulation results conducted using 0.18‐μm CMOS technology and a ±0.9‐V supply voltage align closely with the theoretical predictions. Furthermore, Monte Carlo simulations and corner analysis are employed to evaluate the circuit's robustness. To validate the feasibility of the proposed solution, experimental tests are performed using commercially available components. The designs are implemented on Cadence Virtuoso, and post‐layout measurements are conducted to further verify the proposed solutions.

Low-Frequency Electronically Tunable Fractional Filter and its Implementation as Neural Network

A fractional low-pass filter operating in a low-frequency range is necessary for the filtering of biomedical signals. Thus, we propose a fractional low-pass filter of order ([Formula: see text]) which is implemented using a current follower transconductance amplifier (CFTA). The presented structure is compact. It comprises of five CFTAs along with three grounded capacitors and two resistors. Additionally, this filter structure can be electronically tuned for its order and frequency variation, and these tunings are independent of each other. This electronic tuning is established through the bias current of the active component used. The layout of the proposed filter was designed in Cadence Virtuoso, covering 7920[Formula: see text][Formula: see text]m2 of chip area. It is operating at ±900[Formula: see text]mV with a power consumption of 6.8[Formula: see text]mW. In the simulation results, both pre-layout and post-layout results are included, which indicates that the design is appropriate for fabrication. To check robustness, PVT analysis, Monte-Carlo analysis and THD are also performed. The proposed circuit has also been tested through experiment and its results are also presented. The proposed filter is used to implement a Leaky-Integrate-and-Fire neuron model.

Electronically tunable grounded inductance simulators and capacitor multipliers realization by using single Current Follower Transconductance Amplifier (CFTA)

Electronically tunable grounded inductance simulators and capacitor multipliers realization by using single Current Follower Transconductance Amplifier (CFTA)

Performance Enhancement of Current Follower Transconductance Amplifier (CFTA) and its Application as Filter

This paper presents a modified Current Follower Transconductance Amplifier (CFTA). It provides the essential features of high transconductance, wide bandwidth besides a wide linear range. It records the highest transconductance of 18.2[Formula: see text]mS and power dissipation of 1.12[Formula: see text]mW. Moreover, the linear range ([Formula: see text] versus [Formula: see text]) of CFTA is found as [Formula: see text][Formula: see text][Formula: see text]A. All these essential performance parameters are found much better than the available literature. As an application, a novel second-order universal filter is implemented using the proposed CFTA. It is found that the performance of the filter improves with the use of the proposed CFTA.

Electronically tunable CFTA based positive and negative grounded capacitance multipliers

This paper presents four novel lossless grounded capacitance multiplier (GCM) circuits based on Current Follower Transconductance Amplifier (CFTA). Two of the proposed GCMs are positive and two are negative. The proposed GCMs include two CFTAs, two resistors, and a capacitor. The proposed GCMs employ a minimum number of passive components and do not require any passive element matching condition. The multiplication factor can be controlled either by bias current or by varying either of the two resistances. The effects of parasitic elements on the operating frequency range of the proposed GCMs have been investigated through mathematical analysis. Time and frequency domain analysis has been performed with LTspice program using 0.13 µm IBM CMOS technology parameters. The capacitance cancellation circuit and current-mode universal biquad filter applications are provided to demonstrate the usefulness of the circuit. Monte Carlo and temperature analyses have been performed to verify the robustness of the proposed GCMs. Additionally, comparison of the proposed GCMs with the relevant circuits previously reported in the literature is presented. An experimental example is provided to verify the time-domain performance of the proposed positive lossless GCM by using commercially available integrated circuits (ICs).

Resistorless Memristor Emulator Using CFTA and Its Experimental Verification

This article presents a novel charge-controlled memristor emulator circuit. The proposed memristor emulator utilizes a single Current Follower Transconductance Amplifier (CFTA) as an active current mode analog building block and a grounded capacitor as a passive element. The circuit presented follows all the fingerprints of an ideal memristor. It operates in both incremental as well as decremental mode. The functional performance of the emulator circuit is verified at different operating frequencies and performs well up to 9 MHz . The theoretical and non-ideal analyses are verified for the proposed emulator. Moreover, Monte Carlo sampling and non-volatility analysis are performed to investigate the robustness of the emulator circuit. The functionality of the proposed model has been verified through PSPICE simulation using TSMC 0.18 $\mu m$ CMOS technology at the supply voltage of $\pm 1.2~V$ . The experimental confirmation of the presented circuit is also performed by building a breadboard micromodel using ICs CA3080 and AD844AN. Memristor based Chua’s circuit model is included as one of its applications.

Electronically tunable current-mode multifunction filter using current-controlled current follower transconductance amplifier

A new electronically tunable current-mode multifunction universal filter with three inputs and one output based on current-controlled current follower transconductance amplifier is presented. The proposed filter can realize low-pass, band-pass, high-pass, band-stop and all-pass filtering functions into single topology. For realize these filtering functions, no passive component-matching conditions, no inverting-type input signal requirements and high-output impedance are possessed. Also the proposed filter offers electronic control of the natural angular frequency, low active and passive sensitivities and use of grounded capacitors which is ideal for integrated circuit implementation. The proposed universal biquadratic filter has been used to realize sixth-order filters. PSPICE simulation results are used to confirm the presented theory.

Realization of DTMOS based CFTA and multiple input single output biquadratic filter application

Analog filters can be found in everything from mobile phones to disk drives, from audio systems to power supplies, from telecommunications to broadband internet connection. Analog filters can be formed from a variety of active elements. In this study, the Dynamic Threshold Voltage MOSFET (DTMOS) based Current Follower Transconductance Amplifier (CFTA) active element has been suggested and a multi input single output (MISO) universal biquadratic filter has been obtained with this active element. The proposed circuit operates with ±0.2 V supply voltages and consumes 140 µW power and electronically tunable. All five filtering responses have been realized by selecting the different input signals. All simulations have been performed with LTSpice program using the Predictive Technology Model (PTM) 45 nm Level 54 CMOS process parameters. Analysis of AC/DC, noise, Monte Carlo, temperature, total harmonic distortion (THD) proves that the circuit operates in harmony with the theory. With Monte Carlo analysis, it has been observed that the filter achieves stable output against both passive element and process parameter tolerance. It is hoped that the proposed active element and the filter will be useful in ultra-low voltage, low power, and low frequency analog signal applications.

An Electronically Controllable Fractional Multivibrator

In this study, a fractional capacitor order of α-based new fractional multivibrator topology is proposed. The new proposed circuit consists of a multioutput current follower transconductance amplifier (MO-CFTA) and a grounded fractional capacitor. The proposed topology offers electronically and independently control of output waveform amplitude, trigger levels, and oscillation period via relevant bias currents. The proposed circuit provides higher oscillation frequency in comparison with normal multivibrator. The proposed circuit is simulated via SPICE and 0.18 µm TSMC technology parameters. Furthermore, the introduced concepts are also verified experimentally.

Current-mode universal filter and quadrature oscillator using current controlled current follower transconductance amplifiers

This paper presents a new current-mode quadrature oscillator and universal filter that employs two current controlled current follower transconductance amplifiers and two grounded capacitors. The proposed circuit can be realized either as a quadrature oscillator or as a universal filter without changing circuit topology. In case the circuit works as a quadrature oscillator, the condition and the frequency of oscillation can be independently and electronically controlled. Four-phase quadrature current outputs and two-phase quadrature voltage outputs can also be obtained. In case the circuit works as a universal filter, low-pass, high-pass, band-pass, band-stop and all-pass filtering functions can be obtained simultaneously by appropriately selecting the input and output signals. The natural frequency and the quality factor of filter can also be obtained independently and electronically. PSPICE simulation results are used to verify the workability of the new topology.

A new CMOS design of high transconductance current follower transconductance amplifier and its applications

In this work, a new CMOS implementation of high transconductance current follower transconductance amplifier (CFTA) is proposed. The proposed CFTA uses current starving technique along with an auxiliary unit (AU) to enhance transconductance performance. The cross-drain-coupled MOSFETs are also used in AU which further enhances transconductance of proposed circuit. The proposed CFTA provides higher transconductance and wider tuning range without affecting its output swing and bandwidth performance. The proposed CFTA provides transconductance of 11.3 mS, dissipates 1.8 mW power and operates at ± 0.6 V supply voltage. A current mode third order quadrature oscillator and biquad filter have been designed and simulated, to validate the performance of proposed circuit. The workability of proposed CFTA and its applications have been verified by using Cadence virtuoso schematic composer with TSMC 0.18 µm process parameters.

Design and analysis of high Transconductance Current Follower Transconductance Amplifier (CFTA) and its applications

A high transconductance Current Follower Transconductance Amplifier (CFTA) is proposed in this paper. The proposed CFTA consists of current follower and transconductance stage with NMOS cross-coupl...

Design of Voltage Mode 6th Order Elliptic Band-pass Filter Using Z-Copy Current Follower Transconductance Amplifier )ZC-CFTA(

This paper describes the realization of the new configuration of an active element namely, Z Copy Current Follower Transconductance Amplifier (ZC-CFTA). In this study, the elliptic 6th order voltage-mode (VM) Band-pass filter was configured based on the ZC-CFTA, which operates at a high frequency of about 30 MHz. The active element also contains floated and grounded inductance with one capacitor. The ZC-CFTA which is an ABB (Active Building Block) is configured with a passive element that is the 6th order elliptic Band Pass Filter. The results LT-SPICE software simulation using 0.18µm CMOS processing parameter show that the designed filter could be operated at a supply voltage of 0.9V and it offers the advantages of a small size and high gain.

Single CFTA Based Current-Mode Universal Biquad Filter

This paper introduces a new current-mode (CM) universal biquad filter structure with optimum number of active and passive elements. In the design, the proposed circuit uses a single active element namely, current follower trans-conductance amplifier (CFTA) and two grounded capacitors as passive elements. The main feature of the proposed circuit is that it can realize all five standard filtering functions such as low pass (LP), band pass (BP), high pass (HP), band stop (BS) and all pass (AP) responses across an explicit high impedance output terminal through the appropriate selection of three inputs. In addition, the same circuit is also capable to simultaneously realize three filtering functions (LP, BP and HP) by the use of single current input signal. Moreover, the proposed structure is suited for low voltage, low power operations and offers the feature of electronic tunability of pole-frequency and quality factor. Further to extend the utility of the proposed circuit block higher order current-mode filters are also realized through direct cascading. A detailed non-ideal and parasitic study is also included. The performance of the circuits has been examined using standard 0.25 μ m CMOS parameters from TSMC.

First–Order Transfer Sections with Reconnection–Less Electronically Reconfigurable High–Pass, All–Pass and Direct Transfer Character

Abstract Presented research introduces active filtering circuits which allow change of the transfer type without necessity of reconnection of the input or output terminal that can be very useful for on-chip applications. Our attention is focused on simple first-order filters that allow high-pass response (HP), all-pass response (AP) and also direct transfer (DT) with constant magnitude and phase characteristics between two terminals (input and output) by adjusting of one controllable parameter (current gain B in our case). Useful modification of the well-known current follower transconductance amplifier (CFTA), the so-called Z-copy current-controlled current follower differential input transconductance amplifier (ZC-CCCFDITA) and adjustable current amplifier were utilized in these circuits. Interesting possibilities (crossing between several transfer functions) of presented circuits require different values of B to obtain desired transfer function that is very important for practice and selection of specific way of control. Requirements on value of this continuously controllable gain B differ among presented structures. Theory is supported by simulation and measurement results with behavioral models utilizing commercially available active elements and simulation results with active elements based on CMOS models.

Current-Controlled CFTA Based Fractional Order Quadrature Oscillators

This paper presents a study of fractional order quadrature oscillators based on current-controlled current follower transconductance amplifiers (CCCFTA). The design realisation and performance of the fractional order quadrature oscillators have been presented. The quadrature oscillators are constructed using three fractional capacitors of orders α = 0.5. The fractional capacitor is not available on the market or in the PSPICE program. Fortunately, the fractional capacitor can be realised by using the approximate method for the RC ladder network approximation. The oscillation frequency and oscillation condition can be electronically/orthogonally controlled via input bias currents. Due to high-output impedances, the proposed circuit enables easy cascading in current-mode (CM). The PSPICE simulation results are depicted, and the given results agree well with the anticipated theoretical outcomes.

Voltage-Mode CFTA-C Third-Order Elliptic Low-Pass Filter Design and Optimization Using Signal Flow Graph Approach

In this work, two active only grounded-C equivalents of third-order voltage-mode (VM) elliptic low-pass (LP) LC ladder prototype are proposed. As active building blocks (ABBs) the recently introduced current follower transconductance amplifier (CFTA) were used. The first active only grounded-C LP filter employing eight CFTAs was proposed by interconnecting CFTA-based active equivalent sub-blocks of passive components, where one of the low-impedance input terminals is not used. Since such feature may cause some noise injection into the proposed circuit, the proposed filter was optimized using Mason-Coates' signal flow graph approach. In several steps the number of ABBs was reduced by two and the unused input terminal was eliminated. The performance of the novel and optimized active only grounded-C third-order VM elliptic LP filter was tested experimentally using the readily available UCC-N1B integrated circuit. DOI: http://dx.doi.org/10.5755/j01.eee.21.2.11508

History, Progress and New Results in Synthetic Passive Element Design Employing CFTAs

After the presentation of the Current Follower Transconductance Amplifier (CFTA) active element, it has found a numerous application possibilities while designing linear and non-linear analog function blocks. This paper gives a short review of the CFTA and mainly focuses on the synthetic floating and grounded passive element design, which can also be electronically controllable. Except the design of synthetic inductors, also possible realizations of floating and grounded capacitors and resistors are described, where the value of these passive elements can be adjusted by means of active elements’ parameters. For the design of the corresponding circuit realizations, the Mason-Coates signal flow graph approach is used. The performance of some discussed synthetic elements is verified and evaluated by Spice simulations on simple analog frequency filters.

Realization of a New Current Mode Second-Order Biquad Using Two Current Follower Transconductance Amplifiers (CFTAs)

A new circuit for realization of universal current-mode filter using current Follower Transconductance Amplifiers (CFTAs) is presented. The proposed circuit realizes current-mode low pass, high pass and band pass filter functions simultaneously with a single current source at the input. The band reject and all pass filters can also be obtained from the proposed circuit without any extra hardware. The proposed circuit employs three passive grounded elements and two CFTAs. Linear electronic control of natural frequency ω0 is available in the proposed circuit. The quality factor can be independently adjusted through grounded resistor. The proposed circuit employs two grounded capacitors and a grounded resistor along with two CFTAs. The grounded resistor can be replaced by an OTA based circuit for linear electronic control of quality factor Q0. The circuit exhibits low active and passive sensitivities for ω0 and Q0. Simulation results are obtained using PSPICE software which is in conformity with the theoretical findings.